Recently, in the field of a computer, communication equipment and the like, development of an inductor, a transformer and a coil have been desired, which are suitable for high frequency use (for example, 100 KHz to several hundreds GHz).
In development of the inductor, power transformer and coil, the technical problems of how to decrease the loss in a high frequency band, how to decrease extraneous magnetic radiation, how to stabilize the frequency characteristic of the inductance, and how to enable low-cost production and the like have to be solved.
Conventionally, in order to reduce the loss in a high frequency band, in inductances, transformers and coils of this kind, importance has tended to be placed on development of core materials with high quality which satisfy various performances (for example, low hysteresis loss, and the like) required of the cores (for example, see Patent Document 1).
Further, in order to reduce extraneous magnetic radiation in the inductances, transformers and coils of this kind, the device which pays attention to the shapes of the core and winding has been made (for example, see Patent Document 2).    [Patent Document 1] Japanese Patent Laid-Open No. 2001-237136    [Patent Document 2] Japanese Patent Laid-Open No. 2004-172517